The company's shares were up more than 7 percent at $68.54
in early trading on the New York Stock Exchange.

New York-based Sandell said it believed SemGroup was worth
$104 per share.

Oil prices have declined by more than half since June last
year, primarily driven by a global supply gut.

The plunge in prices could lead to a rash of M&A activity in
the North American oil and gas sector as companies look for
attractive deals at lower prices, analysts have said.

Sandell said it believed there were a number of potential
buyers who could be interested in the company's assets in the
Montney and Duvernay Canadian shale basins and its U.S.
mid-continent gas gathering and processing facilities.

Sandell's estimated value of the company is more than double
the stock's intrinsic value of $42.58, according to Thomson
Reuters StarMine.

The value is calculated using analysts' five-year earnings
estimates and modeling the growth trajectory over a longer
period of time.

Shares of the Tusla, Oklahoma-based company have lost nearly
17 percent of their value in the last six months.
(Reporting by Narottam Medhora in Bengaluru; Editing by
Saumyadeb Chakrabarty)